Non-clumping crystalline cat litter is a cheap source for the exact same silica crystal used in commercial desiccants. Make a bundle with a single layer of cheese cloth and toss it in to the bottom of your chest freezer.
Every few weeks, spray the inside of the freezer down with Starsan and you should be good to go. You can also help yourself by cleaning any wort drips off of the outside of your fermenter.
Last edited by danielbt; 10-05-2012 at 08:19 PM.
Reason: Corrected type of desiccant.